Explanation:

- "I saw the movie last night."

- When you use "the," it implies that both the speaker and the listener know which specific movie is being referred to. It's definite.

- Correct answer here if a specific movie is known.

- "I saw a movie last night."

- "A" is used for something non-specific or when mentioning something for the first time. If the movie is not known or specific, this would be appropriate.

- Correct Answer: if any random movie was seen.

- "I saw an movie last night."

- Incorrect because "an" is used before words that start with a vowel sound. Since "movie" starts with a consonant sound, "an" is inappropriate.

- "I saw one movie last night."

- Using "one" emphasizes the quantity. It would be suitable if the focus is on the number watched rather than general or specific identification.